I had a Ref 1 once and it had the stock tubes in it from Audio Research. I loved that preamp except for a mid-bass bloat sometimes that was too irritating. I got the Ref 2 Mk2 and the bloat disappeared. If not for the bloat, I prefer the Ref 1 over the Ref2 mk2.
Maybe tube rolling would have solved the problem....I just didn't have the patience to experiment with tube rolling. Funny thing though, I didn't get the mid-bass bloat when listening to my tuner though. My tuner took on a whole 'nother dimension with the Ref 1. The Ref 1 sounded better with my tuner than the Ref2 mk2 does now.
Maybe tube rolling would have solved the problem....I just didn't have the patience to experiment with tube rolling. Funny thing though, I didn't get the mid-bass bloat when listening to my tuner though. My tuner took on a whole 'nother dimension with the Ref 1. The Ref 1 sounded better with my tuner than the Ref2 mk2 does now.